Abstract

This work demonstrates the deposition of molybdenum in a deep eutectic solvent for the first time, and explores the processes needed for electrorefining of molybdenum. The electrochemical and transport behavior of chloride-coordinated molybdenum in ethaline was initially studied to determine if deposition was possible. Cyclic voltammetry was used to show that MoCl5 added to ethaline exhibits quasi-reversible behavior. Both the measured transfer coefficient and the precipitation of MoCl3 suggest that the reduction of MoCl5 in ethaline is a two-electron transfer reaction where the oxidation state of molybdenum in the product is Mo(III). No deposit was formed with the use of MoCl5 alone and the presence of a shuttling reaction may be partly responsible for the lack of a deposit. However, the deposition of molybdenum was accomplished in ethaline at 80 °C by altering the speciation of the metal complex with the introduction of fluoride ions. A change in coordinating ligands in the presence of fluoride was evidenced by a change in the electrochemical behavior of the Mo species, as determined with cyclic voltammetry. Chronoamperometry was then used to produce Mo deposits on nickel substrate in the presence of fluoride ion. The deposits were imaged with SEM and the presence of Mo was confirmed with EDX. In order to study the effect of the newly introduced fluoride ion on the anodic dissolution of molybdenum in ethaline, linear sweep voltammetry was used. In addition, a chloride-free electrolyte composed of 1M KF in ethylene glycol was used to anodically dissolve Mo at a faradaic efficiency of 63%. The ability of Mo to be anodically dissolved in the presence of fluoride showed the addition of fluoride enables Mo deposition without significantly hindering the anodic dissolution of Mo. Thus, both dissolution and deposition of molybdenum are possible in a deep eutectic solvent, opening the way for possible development of a Mo electrorefining process.

Degree

College and Department

Ira A. Fulton College of Engineering and Technology; Chemical Engineering

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